If you are going to be around Buenos Aires between the 21st of January and the 16th of March then this might be an option for you.
Konex will be hosting movies in the outdoors. They will supply the drinks and the stars and maybe some chairs. I saw some pictures where there was a lot of people sitting on the floor.
I would call and ask if you can bring your own lawn chair unless you don't mind sitting on concrete for a couple of hours.
Read all about it at their blog called Cine con Estrellas.